±Free
Poisson probability
Compute exactly k and at most k events for a given expected event count.
Enter the expected number of events λ for a fixed interval and the count k. The calculator evaluates e^(−λ) × λ^k / k! and sums probabilities from zero to k.
How to use
- Enter your text, values, or image.
- Adjust the options and run the tool.
- Copy or download your result.
Worked example
Example input
Expected events λ: 1 Observed events: 0
Example result
{
"exactly": 0.367879441171,
"atMost": 0.367879441171
}Limitations and details
λ and k are limited to 10000; a Poisson model assumes an appropriate constant event rate, and extreme probabilities may underflow.
Inputs and options
- Expected events λ
- Number · Minimum: 0 · Maximum: 10000
- Observed events
- Number · Minimum: 0 · Maximum: 10000
Frequently asked questions
Is this tool free and private?
Yes. All 300 tools are free in this phase. Processing happens in your browser; your input and files are not sent to our servers.